Conventionally, various cooling devices or cooling units for cooling an electronic device are being supposed (for example, see Japanese Patent Application Publication No. 2014-183107 and Japanese Patent Application Publication No. 2013-26526). For example, it is supposed that coolant is circulated on a heating component such as a CPU (Central Processing Unit) in order to independently cool electronic devices arrayed in a layered shape, as in a case of a server using a rack mount method (for example, see Japanese Patent Application Publication No. 2008-509542). In this manner, in a method of cooling an electronic device by circulating coolant, it is possible to respond to a condition that an air cooling fan for independently cooling electronic devices arrayed in a layered shape cannot be mounted and a condition that the number of electronic devices arrayed in a layered shape increases.